Labral Tears of the Shoulder: A Concise Overview

Introduction

The labrum is a cartilaginous structure on the glenoid that deepens the shoulder socket, enhances stability, and serves as an attachment point for ligaments and the long head of the biceps tendon. It also provides a 'suction-cup' effect to the joint. Its outer portion is vascularized, while the inner part is mostly avascular.

The clockface analogy is a widely used method to describe and examine the glenoid labrum of the shoulder. In this analogy:

1. The superior portion of the labrum is positioned at 12 o'clock
2. The inferior portion is at 6 o'clock
3. The anterior portion is at 3 o'clock
4. The posterior portion is at 9 o'clock

This orientation is used for both shoulders by convention. Using this analogy, the labrum can be divided into six anatomic quadrants or zones:

1. Superior (11-1 o'clock)
2. Anterosuperior (1-3 o'clock)
3. Anteroinferior (3-5 o'clock)
4. Inferior (5-7 o'clock)
5. Posteroinferior (7-9 o'clock)
6. Posterosuperior (9-11 o'clock)

The region from 10 o'clock to 3 o'clock (posterosuperior, superior, and anterosuperior quadrants) is an area of considerable anatomic variability. This variability can lead to MRI findings that may be misinterpreted as labral pathology.

Diagram shows the clock-like division of the glenoid rim and its four sectors: inferior, posterior, anterior and superior. (Image credit: Jarraya et al., Insights Imaging. 2016)

Types of Labral Tears by Location

Superior Labral Quadrant

The superior labrum exhibits a looser attachment to the glenoid, facilitating increased mobility during overhead movements. This anatomical feature is particularly relevant when discussing Superior Labrum Anterior to Posterior (SLAP) tears, a significant category of labral injuries.

The superior portion of the labrum serves as the attachment point for the long head of the biceps tendon. SLAP tears are thought to occur through a "peel-back" mechanism. In this process, the biceps tendon's attachment to the superior labrum causes the labrum to be gradually "peeled" away from the glenoid rim in a posterior direction.

For a comprehensive understanding of SLAP tears, it's essential to consider their classification. The Snyder classification system, which is widely used and recognized, categorizes SLAP tears into four main types (I through IV). This classification provides a framework for understanding the varying degrees and characteristics of these injuries, aiding in diagnosis and treatment planning.

Type I. Fraying of the labrum without a tear in the superior portion of the glenoid labrum and there is no tear of the biceps tendon

Type II. Fraying with striping the superior labrum from the glenoid and biceps attachment. 

Based on Morgan criteria can be further differentiated into A, B, and C.

1.  Anterior extension of tear
2. Posterior extension of tear
3. Anterior and posterior extension of tear

Type III. Bucket-handle tear of the labrum

Type IV. Bucket-handle tear of the labrum that extends into the biceps tendon

Additional labral tear variations have been described as follows:

Type V. This type combines a Bankart lesion with a Type II SLAP tear. It involves an anteroinferior tear of the glenolabral complex that extends to the superior labrum and biceps tendon, typically spanning from the 11 o'clock to 5 o'clock position. Type V tears are often associated with anterior shoulder dislocations and may present with a coexisting Hill-Sachs lesion.

Type VI. A Type VI tear combines a Type II SLAP lesion with an unstable labral flap. MRI reveals an anterior or posterior flap tear of the labrum with superior biceps tendon stripping. This complex labral tear is located at the 11 to 1 o'clock position, featuring a small torn labral fragment partially attached to the labrum body. These lesions can result from falls on an outstretched hand.

Type VII. This type presents as a Type II superior labral tear extending anteriorly to involve the middle glenohumeral ligament. The tear spans from the 11 to 3 o'clock position and may occur due to acute trauma associated with anterior shoulder dislocations.

Type VIII. Type VIII tears involve a superior labral tear extending to the posteroinferior labrum. More extensive than a Type IIB lesion, it affects the labrum from the 7 to 1 o'clock position. These tears are typically associated with acute posterior shoulder dislocations.

Type IX. This extensive tear results in complete or near-complete detachment of the labrum from the glenoid. It involves both anterior and posterior extension of a superior labral tear, spanning from the 7 to 5 o'clock position. Type IX tears are caused by severe acute trauma.

Type X. Type X combines a superior labral tear with extension to the rotator cuff interval, which may involve the superior glenohumeral ligament or the coracohumeral ligament.

These advanced classifications help surgeons better understand the extent of labral damage and guide appropriate treatment strategies for complex SLAP lesions.

Anterior Labral Quadrant

Pathology affecting the anteroinferior glenoid region encompasses a group of injuries known as Bankart lesions and their variants. These injuries typically occur during anterior shoulder dislocations and involve various degrees of labral avulsion.

The classic Bankart lesion presents as an avulsion of the anteroinferior labrum from the glenoid rim. However, several variants exist, each with distinct characteristics:

1. Perthes lesion: A nondisplaced tear of the anteroinferior labrum where the scapular periosteum remains intact but is stripped medially.
2. Anterior Labroligamentous Periosteal Sleeve Avulsion (ALPSA): Similar to a Bankart lesion, but the labrum and periosteum roll up and displace medially and inferiorly, often referred to as a "medialized Bankart.”.
3. Glenolabral Articular Disruption (GLAD): An anteroinferior labral tear accompanied by erosion of the adjacent articular cartilage.

These variants differ in their specific anatomical involvement and displacement patterns, which can impact both diagnosis and treatment approaches.

Posterior Labral Quadrant (less common)

Injuries to the posterior labrum, while less frequent than their anterior counterparts, represent a significant subset of shoulder pathologies. These injuries typically result from forces applied to the posterior capsule, which can lead to avulsion of the posterior band of the inferior glenohumeral ligament from its labral attachment.

Two main types of posterior labral injuries are noteworthy:

1. Reverse Bankart Lesion: This injury is characterized by a localized tear of the posterior glenoid labrum. It's essentially the posterior equivalent of the more common anterior Bankart lesion.
2. Posterior SLAP Tears: These injuries involve the superior labrum but extend posteriorly. They are considered part of the spectrum of posterior labral pathologies.

The diagnosis and management of posterior labral tears can be challenging due to their relative rarity and the potential for concomitant injuries. Accurate identification and appropriate treatment are crucial for optimal outcomes in patients with posterior shoulder instability or pain.

Inferior Labral Quadrant

The inferior labrum is characterized by its firm attachment to the glenoid, exhibiting less mobility compared to its superior counterpart. This region is involved in several types of labral pathologies:

1. Inferior Bankart Tears: These lesions, primarily classified as anteroinferior injuries, can extend into the inferior quadrant. They are common sequelae of anterior shoulder dislocations.
2. Humeral Avulsion of the Glenohumeral Ligament (HAGL) Lesions: During anterior shoulder dislocations, the anterior inferior glenohumeral ligament (AIGHL) can be avulsed from its humeral attachment. While primarily a ligamentous injury, HAGL lesions may also involve labral damage.
3. Circumferential Labral Tears: These extensive injuries involve a complete or near-complete detachment of the labrum, including the inferior portion.

The involvement of the inferior labrum in these pathologies is significant due to its role in shoulder stability. Accurate diagnosis and appropriate management of inferior labral injuries are crucial for restoring shoulder function and preventing recurrent instability.

Diagnosis and Presentation

The symptoms from a labral tear can present as pain with throwing, or after an acute traumatic injury after falls. Labral tears can be chronic, longstanding labral tears can give rise to paralabral cysts. This is where the tear becomes a one-way valve so joint synovial fluid seeps out of the shoulder joint and not back. Depending on the site of the cyst it can press on surrounding nerves such as the Suprascapular Nerve or Axillary Nerve (Quadrilateral space syndrome). The best way to evaluate a labral tear is with an MRI with intra-articular contrast.

References

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